The present invention primarily relates to backup, or secondary, sump pumps which are battery powered and used in the event of an emergency caused by a failure of a primary sump pump to evacuate the water from the sump. For example, a primary sump pump normally will be powered from the electric line and, perhaps due to the failure of power in the electric lines during a storm, that primary pump will not be operative. The battery powered pump at that time then takes over the task of removing water from the sump. Obviously, such backup pumps operate only infrequently. Yet, they will in many instances be in the sump where they are alternately submerged in water and then free of water, as the water level in the sump goes up and down as a result of the action of the primary pump. This constant bathing of the pump components and then exposing them to air can be particularly hard on the pump components and the mechanical operating condition of the pump, particularly when the pump is normally standing idle. Furthermore, the water moving into and out of the backup sump pump is likely to carry with it contaminates which are deposited on and in that pump further impairing its operating condition.
The principal object of the present invention is to provide a standby pump apparatus such that the water, and any contaminates that it may carry, will be excluded from the operating components of the pump during its period of inaction. Thus there is less opportunity for those operating components to be so deleteriously affected that the pump will fail to operate when it is vitally needed. Just prior to the pump being used, the air column is dissipated and the pump primed.
It is not uncommon for sump pumps to employ a check valve immediately above (or downstream of) the pump. The purpose of this check valve is to prevent the water in the discharge line from draining back into the sump when the pump shuts down. However, in such installations the water below the check valve will not drain out to a significant extent when the pump shuts down. Such a check valve is employed in the present invention, but an air bleeder line is connected below the check valve so that air may be admitted to permit the water below the check valve to be drained out. When the bleeder line is thereafter closed, an air column is then established through the pump. This air column then acts like a diving bell to prevent water from thereafter backing up into the pump to a significant extent. In the present invention this bleeder line is opened just prior to the pump being operated. This permits the air to be expelled and the water to rise in the pump to the level of that in the remainder of the sump. When the pump commences to operate the bleeder line is closed by the valve. This avoids loss of efficiency of the pump.
It is known (U.S. Pat. No. 3,246,606) to use a bleeder line to dissipate an air column and permit the priming of an upper pump, of a dual pump unit, when the unit turns on. But that really has no relation to the present invention wherein the bleeder line is controlled.